Method
Soak the lentils in water at room temperature for about 12/16 hours.

Cook the chestnuts in a pot of water for about 50 minutes, 1 hour. When they are cooked, drain and allow to cool, then peel and cut into pieces not very large.

In a saucepan, make a sauce with oil and onion. then add the lentils and broth and cook for about an 'hour and a half (with regard to the amount of stock, regulator you depending if you like more or less liquid). Then add even chestnuts and leeks cut into slices, rosemary and sage and cook for 25/30 minutes. A perfect score cooking, served with a little extra virgin olive oil and a pinch of pepper.